Shielding arrangement for a reed relay



Oct. 29, 1968 R. MORRISON SHIELDING ARRANGEMENT FOR A REED RELAY 2Sheets-Sheet 1 Filed July 1, 1966 irrazaexr United States PatentOfliceThe present invention relates to an improved reed relay carried by' thecurrent paths and wherein capacitive coupling across netizes the reeds,so they come together into electrical contact. Both single-throw anddouble-throw relays have been used in the past.

' In general, reed relays have been controlled current paths.

Another object of the present invention is to provide an improvedelectro-magnetic reed relay structure which may be inexpensivelymanufactured.

Still another object-of is employed, which material is eco- 3,408,601Patented Oct. 29, 196i One other object of the present invention is toprovide an improved relay structure in which nal coupling between opencontacts is reduced.

These and other objects and advantages of the present invention willbecome apparent from a consideration of the following, taken' inconjunction with the drawings, wherein:

' FIGURE 1 is a perspective view of a reed relay constructed inaccordance with the principles of the present invention;

FIGURE 2 is a fragmentary vertical sectional view taken along thecentral axis of the cylindrical structure of FIGURE 1;

FIGURE 3 is a sectional view taken through the structure of FIGURE 1;

FIGURE 4 is a diagrammatic representation of an illustrative structureincorporating the principles of the present invention;

FIGURE 5 is a sectionalized plan and diagrammatic view of an alternativestructure in accordance with the present invention; and

FIGURE 6 is a diagrammatic representation of a system incorporating astructure somewhat similar that of FIGURE 5.

Referring initially toFIGURE erally cylindrical transversely 1, there isshown a genbody 12 comprising the reed relay, 14 in one end 16 and aconductor 20 in the other end 18. The conductors A second current paththrough the body 12 is provided by a single integral conductor 26passing through the body 12 parallel the conductors 14 and 20 andprovidductors 28, one pair and 20 of the body 12, provide shield memberswithin the body 12.

Functionally, the illustrative component represented in FIGURE 1switches current flow (open or closed circuit) between the conductors 14and 20 in accordance with a tion 31 (FIGURE 2) as shown connecting tact32' to the conductor 20, outside the enclosure 34.

Various forms of reed contacts are well known in the prior art.Generally they are formed of a strip of flexible or resilientlydeformable paramagnetic metal and are shaped to be disconnected (FIGURE2) when in a quiescent state. Upon the applica'tion of the switchingcurrent to the component, a magnetic switching field is developed andthe contacts 30 and 32 move into aligned electrical contact.

The enclosure 34 housing the contacts 30 and 32 is of generallycylindrical configuration and may be formed of'glass, havingglass-to-metal seals in the ends thereof to support the reed contacts 30and 32 and pass them to their respective junctions 31. The solidconductor 26 (FIGURE 2) operates in cooperative relationship with thereed contacts 30 and 31, lies contiguous to the glass enclosure 34 andis encompassed by a cylinder 36 of insulating material of a flexible orresilient nature, e.g. Mylar. Concentric cylinders are then placed aboutthe insulating cylinder 36 to provide spaced-apart co-axial shields inthe component structure. More specifically, in their order of occurrencefrom the cylinder 36, the following cylinders are provided; a conductingcylinder 38; an insulating cylinder 40; a conducting cylinder 42 and aninsulating cylinder 44.

The insulating cylinders all may be similar (in material and form) tothe cylinder 36, e.g. comprising Mylar. The conducting cylinders 38 and42 may comprise a conducting fiber or paper material which has aspecific resistance across points in any given area relationship. Oneexample of a material suitable for the cylinders 38 and 42 ismanufactured by the Minnesota Mining and Manufacturing Company, and isdesignated resistance or conductive paper X1175. The use of conductivepaper in this application is not only economical in cost and fabricationbut also provides shielding of an effective nature in the structurehereof.

Pursuing consideration of the detailed structure of the componentelement, the conductive cylinders 38 and 42 are connected at each end tothe conductors 28 for providing individual electrical contact outsidethe body 12. Additionally, a conductor 28a (FIGURE 2) extends throughthe body, parallel the cylindrical axis and between the cylinders 36 and38, connected at both ends to the conductors 28.

Electrical conductors 22 and 24 (FIGURE 1) for carrying switchingsignals, are connected to a cylindrical coil 46 (FIGURE 3) providedoutside the cylinder 44 in concentric relationship to the othercylinders. The coil 46 provides the magnetic field to displace the reedfor switching operations.

The concentric electrical structure (FIGURE 2) as described above ishoused or embedded in a closure 48 which may comprise epoxy resin orvarious other insulating materials. Thus, the structure is substantiallyisolated from the effects of ambient environments.

In the manufacture of the component as shown in FIGURES l, 2 and 3 thecentral structure may be formed as a sub-assembly providing the reedcontacts 30 and 32 sealed in the glass enclosure 34 with connectingjunctions 31 to the conductors 14 and respectively by using various wellknown techniques of the prior art. Next, the concentric cylinders may beprovided about the enclosure 34 with the conductors 26 and 28a held inposition therein. In this regard, a single wrap of the various materialsconsidered may be provided wtih seams 50 as shown in FIGURE 3 toaccomplish the cylinders. It may be desirable to angularly offset thevarious seams 50 to provide space compensation; however, such aconsideration is only of incidental significance hereto.

The sheets forming the conductive cylinders 38 and 42 carry connectiontabs 52 and 54 (FIGURE 2) at each end which are in turn connected to theends of the conductors 28a and the interconnected conductors 28. Moreoutputterminals 70. The transducer specifically, a conductive adhesive55 is applied to. asmall area of the sheets comprising the cylinders 38and 42 by which the conductive tabs 52 and 54 are then affixed to thecylinders. The tabs 52 and 54 may comprise small sheets of copper orother conductiversheets which provide a base connection for theconductors 28 and28a, This connection may be provided by soldering or'various other techniques well known in theprior art.

Upon completion of the. internaLcylindrical sub-assembly as describedabove, the coil 46 is telescopically positioned thereon. The coil may bepre-wound as a subassembly and placed on the cylindrical assembly, or itmay be wound directly on the partial assembly. The coil 46 is connectedto the energizing conductors 22v and 24 as previously explained. Next,the assembly is encapsulated within the closure 48 as with epoxy pottingcompound, so that the extending conductors lie outside the closure.

Thus, the component is completed and ready for use. As;indicated above,the reed contacts 30 and 32 (FIG- URE 2) are formed to lie spaced apartin the quiescent state of operation; however, upon application asufficinet electrical current to the coil 46 through the conductors 22and 24 (FIGURE 1) a magnetic field is established. which magnetizes thereed contacts 30 and 32 (FIGURE 2) moving them into aligned engagementand thereby closing the circuit between the conductors 14 and 20 (FIG-URE 1). Removal of the magnetic field, by halting current flow in thecoils46, allows the contacts 30 and 32 to spread, opening the circuit.

Considering a particular circuit hereof utilizing the structure hereof,reference will now be made the diagram of FIGURE 4, which illustratesthe shield elements as well as the active signal paths. The reed relayelement as described above is schematically represented in the block 58,the reed contacts 30 and 32 being shown simply as a switch 60. In asimilar schematic fashion, the coil 46 is represented as are theconductive cylinders 38 and The coil 46 (FIGURE 4) is connected througha switch 62 across a source of potential thatis applied to terminals 64.Therefore, closure of the switch 62 energizes the coil 46 to close theswitch 68, thereby completing the signal path from a transducer 66,through an amplifier 68 to 66 is provided within a shield 72 (groundedthrough a capacitor 73)-which also encloses conductors 74 and 76, thatextend to the conductors 14 and 26 respectively, as described withreference to FIGURE 1. The shield 72 is also connected to the cylinder38 and then through conductor 28a. At the amplifier side, a shield 73 isprovided over the amplifier 68 and conductors thereto. The shield 73 isconnected to the through conductor 28a and the cylinder 38 and groundedalong with the cylinder 42.

It is to be noted that the structure hereof enables the use of a groundreturn conductor, i.e. conductor 26, to be used as part of a signalreturn path thereby reducing the magnetic pickup from the operating coilwhich avoids reliance upon the shield structure as a ground return. Thismode of operation is extremely effective in many applications operationwith shields as described.

Regarding the avoidance of spurious signals in the conductors 14, 20 and26 resulting from the energization'of the coil 46, an internalconductive cylinder 38 cooperatively acts as a secondary shield. Infunction, the second shield diverts a second set of shield currents, sothat these currents do not enter the signal-carrying structure. As aresult, significant improvement is provided.

In some applications, capacitive coupling between switch contacts hasbeen found to be a problem. For example, When the switch 60 (FIGURE 4)is open, the reed contacts are capacitively coupled to a degree whichhas been recognized to present a problem. This difficulty can be avoidedby utilization of an alternative embodiment involving critical signals,particularly in cohereof as shown in FIGURES 5 and 6 and as will now beconsidered in detail.

The external coil and shield structure for providing the magnetic fieldin the embodiment of FIGURE 5 and from the support 122 for mutualcontact when the relay is not energized.

' shown, the shield and coil as previously described on the enclosure 92the central placed about the various contacts.

When the relay is in an unenergized state with the two controlled pathstherethrough open (contacts positioned of the reed contacts 110, 114,112 and 116.

Of course, the concepts of the reed relay as illustrated be variouslyembodied gized.

The stationary contact 168 is connected to a movable contact 174 whichcomprises a double-throw switch with and 164. The contact 174 is alsowhich engages the contact 156 when the relay is not energized.

to the shield 144 and to the contact 156. 1

In the operation of the system as shown in FIGURE 5, it is apparent thatwhen the coil 142 is not energized (as depicted) the contacts 152 and154 are not engaged. However, it is also apparent that ists from thesecontacts At a time when the relay coil 142 is energized by applicationof energizing coil, two electrostatic switches in the relay, andprovision of a central section for terminating contact capacitance.

The system hereof also provides a unit which can be set forth below,forming a part of this application.

. 7 What iSclaimediis: i v p 1. A reed relay structure wherein at leastone current path is controlled in accordance with control signals,comprising: a set of re d contacts adapted to be connected in said,current path;

a magnetic coil means for controlling said reed con- I tactsto be openedand closed; p a first conductive shield fixed contacts; I I a secondconductive shield fixed about said first conductive shield; and vinsulation means for ohmically isolating said first and I said secondconductive shields.

2. A reed relay structure according to claim 1 wherein said condi'lctiveshields comprise cylinders of conductive P p r-i ,i V

3. A reed relay structure according to claim 2 further comprisingconnection leads affixed to said conductive paper and wherein saidconductive paper has a resistance of at least ten ohms per inch. 4. Areedrelay structure according to claim I'further including a conductorextending substantially parallel to said set of reed contacts to be usedas a part of the signal return path to reduce the magnetic pickup fromthe operating coil. p i

5. A reed relay structure according to claim 4 wherein said conductiveshields comprise conductive paper having aresistance of at least 10 ohmsper inch and further including terminal conductors atfixed to saidconductive shields.

6. A reed relay structure according to claim 5 further including inputsignal means for providing a signal between said conductor and one ofsaid reed contacts and further including means connecting said firstshield.

about said set of reed 7. A reed relay structure according to claim 2wherein said insulation means comprises a Mylar-like plastic material. iv

8. A reed relay structure according to claim 7, further comprisingconnection leads afiixed to said conductive paper and wherein saidconductive paper has a resistance of at least ten ohms per inch; andfurther including a conductor extending substantially parallel to saidset of reed contacts to be used as a part of the signal return path toreduce the magnetic pickup from the operating coil.

9. A reedfrelay'according to claim 1 including a plurality of sets ofreed contactswhereby when said relay is open, certain of said reedcontacts intermediate other of said reed contacts provide capacitivetermination.

10. A'reed relay'according to claim 1 further comprisinga plurality ofthrough conductors extending through said magnetic coil means.

I 11'. A reed relay according to claim 1 wherein a plurality of currentpaths-therethrough and therefore including additional setsof reedcontacts.

12. A reed relay according to claim 11 including a plurality of sets ofreed contacts whereby when said relay is open, certain of said reedcontacts intermediate other of said reed contacts providecapacitive'termination.

References Cited UNITED STATES PATENTS 3.005069 10/1961 Sippach et al.335-452 3,202,784 8/1965 Santangeli 200-153 XR 3,320,559 5/1967 Morrison335-151 BERNARD A. GILHEANY, Primary Examiner. R. N. ENVALL, 1a.,Assistant Examiner.

1. A REED RELAY STRUCTURE WHEREIN AT LEAST ONE CURRENT PATH ISCONTROLLED IN ACCRODANCE WITH CONTROL SIGNALS, COMPRISING: A SET OF REEDCONTACTS ADAPTED TO BE CONNECTED IN SAID CURRENT PATH; A MAGNETIC COILMEANS FOR CONTROLLING SAID REED CONTACTS TO BE OPENED AND CLOSED; AFIRST CONDUCTIVE SHIELD FIXED ABOUT SAID SET OF REED CONTACTS; A SECONDCONDUCTIVE SHIELD FIXED ABOUT SAID FIRST CONDUCTIVE SHIELD; ANDINSULATION MEANS FOR OHMICALLY ISOLATING SAID FIRST AND SAID SECONDCONDUCTIVE SHIELDS.